Base station, mobile station, communication system, and reordering method thereof

Abstract

A reordering method in a communication system where a base station sends to a mobile station, packets to which numbers indicating a sequence are attached, the mobile station rearranges the packets in order of the sequence numbers, and a hard handover is performed. The method includes deciding whether a handover source base station forwards packets which have not yet been sent to the mobile station, out of packets received from a host station, to a handover target base station; controlling forwarding of the packets at the handover based on the decision, and sending forwarding execution information from the handover source base station to the mobile station to notify whether the forwarding of the packets has been executed; and at the mobile station, receiving the forwarding execution information, and executing reordering of the packets received from the handover target base station based on the forwarding execution information at the handover.

What is claimed is: 
     
       1. A reordering method in a communication system in which a base station sends packets to which numbers indicating sequence are attached, to a mobile station, the mobile station rearranges the packets in order of the sequence number, and hard handover is performed, comprising:
 deciding based on a forwarding policy depending on communication services whether a handover source base station forwards packets which are not sent from the handover source base station to the mobile station, to a handover target base station or not; 
 controlling forwarding of the packets from the handover source base station to the handover target base station at the handover based on the decision, and sending forwarding execution information from the handover source base station to the mobile station to notify whether the forwarding of the packets from the handover source base station to the handover target base station is executed or not; and 
 at the mobile station, receiving the forwarding execution information from the handover source base station, and executing reordering of the packets received from the handover target base station based on the forwarding execution information at the handover. 
 
     
     
       2. The reordering method according to  claim 1 , wherein the forwarding execution information is used by the mobile station for determining whether the mobile station should execute reordering of the packets received from the handover target base station. 
     
     
       3. A reordering method in a communication system in which a base station sends packets to which numbers indicating sequence are attached, to a mobile station, the mobile station rearranges the packets in order of the sequence number, and hard handover is performed, comprising:
 deciding whether a handover source base station forwards packets which are not sent from the handover source base station to the mobile station, to a handover target base station or not; 
 controlling forwarding of the packets from the handover source base station to the handover target base station at the handover based on the decision, and sending forwarding execution information from the handover source base station to the mobile station to notify whether the forwarding of the packets from the handover source base station to the handover target base station is executed or not; and 
 at the mobile station, receiving the forwarding execution information from the handover source base station, and executing reordering of the packets received from the handover target base station based on the forwarding execution information at the handover 
 wherein in a case where the handover source base station is to forward the packets which have not been sent to the mobile station, to the handover target base station at the handover, the handover source base station forwards the packets to the handover target base station at the handover and sends the forwarding execution information which notifies that the forwarding of the packets from the handover source base station to the handover target base station has been executed, to the mobile station, and in a case where the handover source base station is not to forward the packets to the handover target base station at the handover, the handover source base station sends the forwarding execution information which notifies that the forwarding of the packets from the handover source base station to the handover target base station has been not executed, to the mobile station at the handover. 
 
     
     
       4. The reordering method according to  claim 1 , wherein the handover source base station decides whether the handover source base station forwards the packets which have not been sent to the mobile station, to the handover target base station at the handover or not, in conformity with the type of communication call. 
     
     
       5. The reordering method according to  claim 2 , wherein the handover source base station decides whether the handover source base station forwards the packets which have not been sent to the mobile station, to the handover target base station at the handover or not, in conformity with the type of communication call. 
     
     
       6. The reordering method according to  claim 1 , wherein the handover target base station stores both packets received from the host station and the packets received from the handover source base station at the handover in a storage unit and sends the packets stored in the storage unit to the mobile station. 
     
     
       7. The reordering method according to  claim 2 , wherein the handover target base station stores both packets received from the host station and the packets received from the handover source base station at the handover in a storage unit and sends the packets stored in the storage unit to the mobile station. 
     
     
       8. The reordering method according to  claim 7 , wherein the handover target base station sends the packets received from the handover source base station at the handover preferentially and sends the packets received from the host station subsequently. 
     
     
       9. The reordering method according to  claim 1 , wherein the mobile station determines at the handover whether the mobile station executes reordering of the packets received from the handover target base station or not, based the forwarding execution information. 
     
     
       10. The reordering method according to  claim 4 , wherein the mobile station controls the reordering of the packets received from the handover target base station based on the forwarding execution information which is set in conformity with the type of the communication call. 
     
     
       11. The reordering method according to  claim 1 , wherein the mobile station stores the packets received from the handover target base station in a storage unit and performs reordering of the packets stored in the storage unit. 
     
     
       12. The reordering method according to  claim 1 , wherein the mobile station ends reordering processing when packets having continuous numbers are not received even if reordering processing of the received packets is executed for a predetermined time. 
     
     
       13. The reordering method according to  claim 2 , wherein the mobile station ends reordering processing when packets having continuous numbers are not received even if reordering processing of the received packets is executed for a predetermined time. 
     
     
       14. A reordering method in a communication system in which a base station sends packets to which numbers indicating order are attached, to a mobile station, the mobile station performs delivery of the packets in order, and handover is performed, comprising:
 sending configuration information set based on a forwarding policy depending on communication services and indicating whether forwarding of packets which are not sent from a handover source base station to the mobile station is executed or not, to the mobile station; 
 at the mobile station, receiving from the handover source base station, the configuration information indicating whether the forwarding of packets which are not sent from the handover source base station to the mobile station is executed or not; and 
 at the mobile station, controlling delivery of the packets received from a handover target base station at the handover, in order based on the configuration information indicating whether the forwarding of packets which are not sent from the handover source base station to the mobile station is executed or not. 
 
     
     
       15. The reordering method according to  claim 14 , wherein
 the handover source base station decides whether the handover source base station forwards packets which are not sent from the handover source base station to the mobile station, to the handover target base station or not, controls the forwarding of the packets from the handover source base station to the handover target base station at the handover based on the decision, and sends the configuration information indicating whether forwarding of packets has been executed or not, to the mobile station. 
 
     
     
       16. The communication system according to  claim 14 , wherein
 the controller in the handover source base station decides at the handover whether the handover source base station forwards packets which are not sent from the handover source base station to the mobile station, to a handover target base station or not.